Sense 3riddle, screen -- (separate with a riddle, as grain from chaff) => sift, sieve, strain -- (separate by passing through a sieve or other straining device to separate out coarser elements; "sift the flour")

Sense 6riddle -- (explain a riddle) => solve, work out, figure out, puzzle out, lick, work -- (find the solution to (a problem or question) or understand the meaning of; "did you solve the problem?"; "Work out your problems with the boss"; "this unpleasant situation isn't going to work itself out"; "did you get it?"; "Did you get my meaning?"; "He could not work the math problem")

Sense 2riddled -- (spread throughout; "cities riddled with corruption") => full (vs. empty) -- (containing as much or as many as is possible or normal; "a full glass"; "a sky full of stars"; "a full life"; "the auditorium was full to overflowing")